Ultraviolet disinfection system

ABSTRACT

Embodiments of the invention include an ultraviolet (UV) source, the UV source including a semiconductor device comprising an active layer disposed between an n-type region and a p-type region. The active layer emits radiation having a peak wavelength in a UV range. A reflector cup is disposed around the UV source. A transparent cover is disposed over the reflector cup.

BACKGROUND Description of Related Art

The bandgap of III-nitride materials, including (Al, Ga, In)—N and theiralloys, extends from the very narrow gap of InN (0.7 eV) to the verywide gap of AN (6.2 eV), making III-nitride materials highly suitablefor optoelectronic applications such as light emitting diodes (LEDs),laser diodes, optical modulators, and detectors over a wide spectralrange extending from the near infrared to the deep ultraviolet. Visiblelight LEDs and lasers can be obtained using InGaN in the active layers,while ultraviolet (UV) LEDs and lasers require the larger bandgap ofAlGaN.

UV LEDs with emission wavelengths in the range of 230-350 nm areexpected to find a wide range of applications, most of which are basedon the interaction between UV radiation and biological material. Typicalapplications include surface sterilization, water purification, medicaldevices and biochemistry, light sources for ultra-high density opticalrecording, white lighting, fluorescence analysis, sensing, andzero-emission automobiles.

UV radiation has disinfection properties that inactivate bacteria,viruses, and other microorganisms. A low-pressure mercury lamp mayproduce UV radiation in the range of 254 nm. Since most microorganismsare affected by radiation around 260 nm, UV radiation is in theappropriate range for germicidal activity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a UV radiation source 50, including a UV-emittingdevice (UVLED).

FIG. 2 is a plan view of multiple pixels in a flip chip UVLED.

FIG. 3 is a cross sectional view of one pixel in the UVLED of FIG. 2.

FIG. 4 illustrates a UV radiation source 50, including a UVLED and alens.

FIG. 5 illustrates the UV radiation source of FIG. 1 used to disinfectan object spaced apart from the UV radiation source.

FIG. 6 illustrates the UV radiation source of FIG. 1 used to disinfect afluid.

FIG. 7 is a block diagram of a circuit for controlling a UV disinfectionsystem.

DETAILED DESCRIPTION

Though the devices described herein are III-nitride devices, devicesformed from other materials such as other III-V materials, II-VImaterials, Si are within the scope of embodiments of the invention. Thedevices described herein may be configured to emit UV A (peak wavelengthbetween 340 and 400 nm), UV B (peak wavelength between 290 and 340 nm),or UV C (peak wavelength between 210 and 290 nm) radiation.

In embodiments of the invention, one or more UVLEDs are used in apackaged UV radiation source. Though any suitable use for the UVradiation source is contemplated in embodiments of the invention, insome embodiments the UV radiation source may be used in a disinfectiondevice, suitable for disinfecting an object, a fluid such as water orair, or any other suitable material or structure.

FIG. 1 illustrates a packaged UV radiation source 50. In the device ofFIG. 1, one or more UVLEDs 1 are attached to a mount 70. The mount 70may be, for example, a ceramic mount, a circuit board, a metal-coreprinted circuit board, a silicon mount, or any other suitable structure.Circuit elements such as driver circuitry for UVLED 1 or any othersuitable circuitry may be disposed on or within mount 70. A single UVLEDmay be used, multiple UVLEDs disposed in a single package may be used,or multiple packages including one or more UVLEDs each may be used, inorder to provide UV radiation sufficient for a given application.

A reflector cup 32 is disposed around UVLED 1. Reflector cup 32 may beany suitable structure. In some embodiments, reflector cup 32 is ahollow structure that is attached, for example, to the mount 70. Theinner surfaces of reflector cup 32 are reflective to UV radiation. Forexample, reflector cup 32 may be fabricated from a reflective material,such as aluminum, formed by any suitable technique including, forexample, machining and polishing the reflective surfaces. Alternatively,reflector cup 32 may be fabricated from a non-reflective material thatis coated on the inside with a reflective layer. Suitable examplesinclude plastic formed by, for example, molding, injection molding, 3-Dprinting, or any other suitable technique. Examples of suitablereflective coatings include metals, silver, aluminum, Teflon,polytetrafluoroethylene (PTFE), barium sulfate, oxides, oxides ofsilicon including SiO₂, oxides of yttrium, oxides of hafnium, amultilayer stack, a distributed Bragg reflector, and combinationsthereof. The coating may be formed by any suitable technique including,for example, plating, evaporating, or spray coating. The reflectiveinner surface of reflector cup 32 may have any suitable finish includinga mirror finish, a diffusely reflective or “orange peel” finish, or afaceted finish (the facets may have a mirror finish or diffuselyreflective finish).

In some embodiments, reflector cup 32 may create a radiation patternthat is more collimated than the radiation pattern emitted by the UVLED1 without the reflector cup 32. In some embodiments, reflector cup 32 isshaped such that the UV radiation emitted from the device at the top ofreflector cup 32 is substantially uniform. In some embodiments,reflector cup 32 may have parabolic sidewalls. The cross section ofreflector cup 32, in a plane parallel to a major surface of UVLED 1, maybe circular, square, rectangular, oval, or any other suitable shape.Typically reflector cup 32 alters the radiation output pattern by directreflection, though in some embodiments total internal reflection may beused.

A cover 34 is disposed over the reflector cup 32. The cover may be anymaterial that is resistant to radiation emitted by UVLED 1 and opticallytransmissive to radiation emitted by UVLED 1. In some embodiments, thecover 34 is transparent to radiation emitted by UVLED 1. Suitablematerials include but are not limited to quartz, fused silica, UV-hardplastic films such as Fluorinated ethylene propylene (FEP), silicone,sapphire, UV-transparent glass, and UV-transparent cyclic olefincopolymer (COC) sold under the name TOPAS®. The reflecting cup directsthe radiation emitted by UVLED 1 so that it impinges on cover 34 at anangle that is substantially perpendicular to a major surface of cover34, for example to minimize reflection in some embodiments. In someembodiments, the top side of cover 34 (the side facing away from UVLED1), the bottom side of cover 34 (the side facing UVLED 1), or both areroughened, textured, or patterned, for example to act as a diffuser tothe radiation exiting cover 34.

In some embodiments, the area 36 enclosed by UVLED 1, reflector cup 32,and cover 34 is filled with air or other ambient gas. The area 36 may besealed, though this is not required in embodiments where the area 36 isfilled with ambient gas. In some embodiments, area 36 may be filled withan index-matching material such as lens oil, silicone gel, or a solidmaterial such as quartz or silicone. The index-matching material may beselected to match the index of refraction of UVLED 1 (for example, thegrowth substrate of UVLED 1, described below), of cover 34, or may beselected to be between the indices of refraction of UVLED 1 and cover34.

In some embodiments, an optic such as a lens or any other suitablestructure is formed or disposed over UVLED 1, as illustrated in FIG. 4.Lens 38 is formed from a material that is transparent to UV radiation atwavelengths emitted by UVLED 1, and able to withstand the UV radiationwithout degrading. For example, in some embodiments, lens 38 may beformed from a material that transmits at least 85% of UV radiation at280 nm. The material may degrade no more than 1% after 1000 hrs ofexposure to UV radiation at 280 nm. In some embodiments, lens 38 isformed from a material that is moldable, such as, for example, glass,IHU UV transmissive glass available from Isuzu Glass, Inc., andUV-resistant silicone. In some embodiments, lens 38 is formed from amaterial that may be shaped by, for example, grinding and polishing,such as quartz or sapphire. A lens formed by molding may be lessexpensive; a lens formed by grinding and polishing may be of betteroptical quality. A pre-formed lens 38 such as a quartz lens may be isattached to UVLED 1, or disposed over UVLED 1 and attached to mount 70.Lens 38 may be optically coupled to just the top surface of UVLED 1 orto the top and side surfaces of UVLED 1. Lens 38 may be any suitableshape. Though a dome lens is illustrated, other shapes such as Fresnellenses, hyperbolic lenses, parabolic lenses, and lenses with a squarebase or a base the same shape as UVLED 1 (i.e. the bottom surface of thelens, and/or the portion of the lens in contact with the top, emissionsurface of UVLED 1 is square or the same shape as UVLED 1) may besuitable. When a lens 38 is included, area 36 is generally filled withair or other gas, though in some embodiments a liquid, gel, or solid mayfill area 36, as described above.

Commercially available UVA, UVB, and UVC LEDs may be used in the variousembodiments. FIGS. 2 and 3 are examples of the assignee's own UVB andUVC LEDs that may be used. FIG. 2 is a top down view of a portion of anarray of UVLED pixels 12, and FIG. 3 is a bisected cross-section of asingle UVLED pixel 12. Any suitable UVLED may be used and embodiments ofthe invention are not limited to the device of FIGS. 2 and 3.

The UVLEDs are typically III-nitride, and commonly GaN, AlGaN, andInGaN. The array of UV emitting pixels 12 is formed on a singlesubstrate 14, such as a transparent sapphire substrate. Other substratesare possible. Although the example shows the pixels 12 being round, theymay have any shape, such as square. The light escapes through thetransparent substrate, as shown in FIG. 3. The pixels 12 may each beflip-chips, where the anode and cathode electrodes face the mount(described below).

All semiconductor layers are epitaxially grown over the substrate 14. AnAN or other suitable buffer layer (not shown) is grown, followed by ann-type region 16. The n-type region 16 may include multiple layers ofdifferent compositions, dopant concentrations, and thicknesses. Then-type region 16 may include at least one Al_(a)Ga_(1-a)N film dopedn-type with Si, Ge and/or other suitable n-type dopants. The n-typeregion 16 may have a thickness from about 100 nm to about 10 microns andis grown directly on the buffer layer(s). The doping level of Si in then-type region 16 may range from 1×10¹⁶ cm⁻³ to 1×10²¹ cm⁻³. Depending onthe intended emission wavelength, the AN mole fraction “a” in theformula may vary from 0% for devices emitting at 360 nm to 100% fordevices designed to emit at 200 nm.

An active region 18 is grown over the n-type region 16. The activeregion 18 may include either a single quantum well or multiple quantumwells (MQWs) separated by barrier layers. The quantum well and barrierlayers contain Al_(x)Ga_(1-x)N/Al_(y)Ga_(1-y)N, wherein 0<x<y<1, xrepresents the AN mole fraction of a quantum well layer, and yrepresents the AN mole fraction of a barrier layer. The peak wavelengthemitted by a UV LED is generally dependent upon the relative content ofAl in the AlGaN quantum well active layer.

A p-type region 22 is grown over the active region 18. Like the n-typeregion 16, the p-type region 22 may include multiple layers of differentcompositions, dopant concentrations, and thicknesses. The p-type region22 includes one or more p-type doped (e.g. Mg-doped) AlGaN layers. TheAlN mole fraction can range from 0 to 100%, and the thickness of thislayer or multilayer can range from about 2 nm to about 100 nm (singlelayer) or to about 500 nm (multilayer). A multilayer used in this regioncan improve lateral conductivity. The Mg doping level may vary from1×10¹⁶ cm⁻³ to 1×10²¹ cm⁻³. A Mg-doped GaN contact layer may be grownlast in the p-type region 22.

All or some of the semiconductor layers described above may be grownunder excess Ga conditions, as described in more detail in U.S.2014/0103289, which is incorporated herein by reference.

The semiconductor structure 15 is etched to form trenches between thepixels 12 that reveal a surface of the n-type region 16. The sidewalls12 a of the pixels 12 may be vertical or sloped with an acute angle 12 brelative to a normal to a major surface of the growth substrate. Theheight 138 of each pixel 12 may be between 0.1-5 microns. The widths 131and 139 at the bottom and top of each pixel 12 may be at least 5microns. Other dimensions may also be used.

Before or after etching the semiconductor structure 15 to form thetrenches, a metal p-contact 24 is deposited and patterned on the top ofeach pixel 12. The p-contact 24 may include one or more metal layersthat form an ohmic contact, and one or more metal layers that form areflector. One example of a suitable p-contact 24 includes a Ni/Ag/Timulti-layer contact.

An n-contact 28 is deposited and patterned, such that n-contact 28 isdisposed on the substantially flat surface of the n-type region 16between the pixels 12. The n-contact 28 may include a single or multiplemetal layers. The n-contact 28 may include, for example, an ohmicn-contact 130 in direct contact with the n-type region 16, and ann-trace metal layer 132 formed over the ohmic n-contact 130. The ohmicn-contact 130 may be, for example, a V/Al/Ti multi-layer contact. Then-trace metal 132 may be, for example, a Ti/Au/Ti multi-layer contact.

The n-contact 28 and the p-contact 24 are electrically isolated by adielectric layer 134. Dielectric layer 134 may be any suitable materialsuch as, for example, one or more oxides of silicon, and/or one or morenitrides of silicon, formed by any suitable method. Dielectric layer 134covers n-contact 28. Openings formed in dielectric layer 134 exposep-contact 24.

A p-trace metal 136 is formed over the top surface of the device, andsubstantially conformally covers the entire top surface. The p-tracemetal 136 electrically connects to the p-contact 24 in the openingsformed in dielectric layer 134. The p-trace metal 136 is electricallyisolated from n-contact 28 by dielectric layer 134.

Robust metal pads electrically connected to the p-trace metal 136 andn-contact 28 are provided outside of the drawing for connection to powersupply terminals. Multiple pixels 12 are included in a single UVLED. Thepixels are electrically connected by large area p-trace metal 136 andthe large area n-trace metal 132. The number of pixels may be selectedbased on the application and/or desired radiation output. A singleUVLED, which includes multiple pixels, is illustrated in the followingfigures as UVLED 1.

In some embodiments, substrate 14 is sapphire. Substrate 14 may be, forexample, on the order of hundreds of microns thick. In a 1 mm squareUVLED 1 with a 200 μm thick sapphire substrate, assuming radiation isextracted from the top and sides of the substrate, the top surfaceaccounts for about 55% of the extraction surface, and the sides accountfor about 45% of the extraction surface of the substrate. Substrate 14may remain part of the device in some embodiments, and may be removedfrom the semiconductor structure in some embodiments.

In some embodiments, the top, emission surface of substrate 14 isroughened, patterned, or textured, for example to improve extraction ofradiation, or to shape the extraction of radiation from the device. Forexample, micro-lens arrays, one or more Fresnel lenses, or photoniccrystals may be formed in the sapphire substrate. In some embodiments,the opposite, growth surface of the substrate may be roughened,patterned, or textured, for example to facilitate growth and/or toimprove extraction of radiation from the semiconductor material into thesubstrate 14.

The UVLED may be square, rectangular, or any other suitable shape whenviewed from the top surface of substrate 14, when the device is flippedrelative to the orientation illustrated in FIG. 3.

The UV radiation sources 50 illustrated in FIGS. 1 and 4 may beparticularly suited to some disinfection applications. In someembodiments, an object to be disinfected is simply placed on the cover34. FIGS. 5 and 6 illustrate two disinfection applications using the UVradiation sources illustrated in FIGS. 1 and 4.

In the device of FIG. 5, UV radiation source 50 is spaced apart from anobject 64 to be disinfected. The object 64 may be placed on a stage 60.The stage 60 may be placed such that the object 64 is spaced an optimaldistance 62 from the output area of the UV radiation source 50 (i.e.,the surface of cover 34). The distance 62 may be selected for one ormore particular characteristics of the output UV radiation at thatpoint, such as uniformity and/or or radiative power.

In some embodiments, a device 66 for adjusting the distance between theoutput area of UV radiation source 50 and an object 64 placed on stage60 is coupled to the UV radiation source 50, the stage 60, or both. Thedevice 66 may include, for example, a sensor for determining thedistance between the object and the UV radiation source, and a motor formoving one of the UV radiation source 50 and the stage 60 up or down,such that the distance between the object and the UV radiation source isthe optimal distance 62 for disinfection.

In some embodiments, the stage 60 may be configured to move the object64 past the output area of the UV radiation source 50. For example, thestage 60 may be a conveyor belt. One application of the systemillustrated in FIG. 5 is a conveyor belt on which a user places a cellphone, laptop, or other object, such that the object passes under the UVpower emitted from the output surface of UV radiation source 50 and isdisinfected.

In the device of FIG. 6, the UV radiation source is coupled to a chambercontaining liquid or gas to be disinfected. The cover 34 may form a wallof the chamber, as illustrated, or the cover may be optically coupled toa separate wall of the chamber.

FIG. 7 is a block diagram of a circuit, which may control a UV radiationsource in any suitable application such as, for example, thedisinfection applications described above. The number of UV radiationsources 50 and the time needed for disinfection may be easily calculatedas is known in the art. Any suitable circuit may be used. Not all of thecomponents illustrated in FIG. 7 are necessary in all embodiments. Thecomponents may be disposed on or in a mount, described above, andelectrically connected to each other as illustrated via the mount, acircuit board, or any other suitable structure. UV radiation source 50may be connected to a microprocessor 90, which may turn the UV radiationsource 50 on and off, and may adjust the power to UV radiation source50. A switch 91, which may be user-activated or automatic, and may beany suitable switch, may activate the UV radiation source directly (notshown in FIG. 7), or may activate the microprocessor, which turns on theUV radiation source.

The amount of time that a fluid or object is exposed to radiation fromUV radiation source may be dictated by a timer 94, which may count apredetermined amount of time, after which the microprocessor 90 may turnoff UV radiation source 50. An indicator 92, such as a light or anyother suitable indicator, may indicate whether UV radiation source 50 isemitting UV radiation.

A detector 96 may detect an amount of UV radiation at a given point inthe disinfection system. The amount of UV radiation emitted by source 50may be adjusted accordingly by microprocessor 90. A second detector 98may be used to detect whether the UV radiation source 50 is functioningproperly. For example, first detector 96 may be positioned near UVradiation source 50, and second detector 98 may be positioned far fromUV radiation source 50. When UV radiation source 50 is on, the amount ofUV radiation detected by each of detectors 96 and 98 may be compared. Ifdetector 96 indicates a higher amount of UV radiation and detector 98indicates a lower amount of UV radiation, a fluid may be contaminatedwith particulate matter. If detectors 96 and 98 both indicate a lowamount of UV radiation, the UV radiation source 50 may not befunctioning properly. Indicator 92 may be used to indicate to a userthat UV radiation source 50 is not functioning properly.

In one operation, a user activates switch 91. In response,microprocessor 90 turns on UV radiation source 50. Microprocessor 90 mayalso switch indicator 92 to a status indicating the UV radiation sourceis disinfecting. The amount of UV radiation is measured by detector 96.In response, microprocessor 90 may adjust the amount of time that the UVradiation source 50 stays on, and/or the power to UV radiation source50, in order to deliver a sufficient dose of UV radiation to disinfectthe fluid. Once the dose is reached, microprocessor 92 may switch off UVradiation source 50, and switch off indicator 92 or change indicator 92to a status indicating the UV radiation source is finished disinfecting.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. In particular, different features andcomponents of the different devices described herein may be used in anyof the other devices, or features and components may be omitted from anyof the devices. A characteristic of, for example, the optic, describedin the context of one embodiment, may be applicable to any embodiment.Suitable materials described for a particular component in a particularembodiment may be used for other components, and/or in otherembodiments. Therefore, it is not intended that the scope of theinvention be limited to the specific embodiments illustrated anddescribed.

1. A structure comprising: an ultraviolet (UV) source comprising asemiconductor device comprising an active layer disposed between ann-type region and a p-type region, wherein the active layer emitsradiation having a peak wavelength in a UV range; a reflector cupdisposed around the UV source, a surface of the reflector cup facing theUV source comprising a direct, diffuse reflector; and an opticallytransmissive cover disposed over the reflector cup.
 2. (canceled)
 3. Thestructure of claim 1 further comprising a liquid, gel, or solid materialdisposed between the UV source and the optically transmissive cover. 4.The structure of claim 3 wherein the UV source comprises a growthsubstrate, and an index of refraction of the material is between anindex of refraction of the optically transmissive cover and an index ofrefraction of the growth substrate.
 5. A structure comprising: anultraviolet (UV) source comprising a semiconductor device comprising anactive layer disposed between an n-type region and a p-type region,wherein the active layer emits radiation having a peak wavelength in aUV range; a reflector cup disposed around the UV source; and anoptically transmissive cover disposed over the reflector cup, whereinthe optically transmissive cover is oriented to form a stage on which anobject to be disinfected is placed.
 6. A structure comprising: anultraviolet (UV) source comprising a semiconductor device comprising anactive layer disposed between an n-type region and a p-type region,wherein the active layer emits radiation having a peak wavelength in aUV range; a reflector cup disposed around the UV source; and anoptically transmissive cover disposed over the reflector cup, whereinthe optically transmissive cover forms a sidewall of a vessel suitablefor containing a fluid.
 7. A structure comprising: an ultraviolet (UV)source comprising a semiconductor device comprising an active layerdisposed between an n-type region and a p-type region, wherein theactive layer emits radiation having a peak wavelength in a UV range; areflector cup disposed around the UV source; and an opticallytransmissive cover disposed over the reflector cup, wherein theoptically transmissive cover is optically coupled to a sidewall of avessel suitable for containing a fluid.
 8. The structure of claim 1further comprising an optic disposed over the UV source.
 9. A structurecomprising: an ultraviolet (UV) source comprising a semiconductor devicecomprising an active layer disposed between an n-type region and ap-type region, wherein the active layer emits radiation having a peakwavelength in a UV range; a reflector cup disposed around the UV source;and an optically transmissive cover disposed over the reflector cup,wherein a major surface of the optically transmissive cover isroughened.
 10. The structure of claim 1 wherein the opticallytransmissive cover is oriented to form a stage on which an object to bedisinfected is placed.
 11. The structure of claim 1 wherein theoptically transmissive cover forms a sidewall of a vessel suitable forcontaining a fluid.
 12. The structure of claim 1 wherein a major surfaceof the optically transmissive cover is roughened.
 13. The structure ofclaim 5 further comprising a liquid, gel, or solid material disposedbetween the UV source and the optically transmissive cover.
 14. Thestructure of claim 5 wherein a major surface of the opticallytransmissive cover is roughened.
 15. The structure of claim 5 furthercomprising an optic disposed over the UV source.
 16. The structure ofclaim 6 further comprising a liquid, gel, or solid material disposedbetween the UV source and the optically transmissive cover.
 17. Thestructure of claim 6 further comprising an optic disposed over the UVsource.
 18. The structure of claim 6 wherein a major surface of theoptically transmissive cover is roughened.
 19. The structure of claim 7further comprising an optic disposed over the UV source.
 20. Thestructure of claim 9 further comprising a liquid, gel, or solid materialdisposed between the UV source and the optically transmissive cover. 21.The structure of claim 9 further comprising an optic disposed over theUV source.